1. Field of the Invention
This invention relates to ex-situ monitoring of pressure in a closed vessel containing fluid, and in a preferred aspect to ex-situ monitoring of pressure in a fluid storage and dispensing system from which a gas or liquid can be dispensed for use in the manufacture of semiconductor devices and materials.
2. Description of the Related Art
In a wide variety of industrial processes and applications, there is a need for a reliable source of process fluid(s).
For example, a safe, reliable and efficient fluid supply source is desirable in the fields of semiconductor manufacturing, ion implantation, manufacture of flat panel displays, medical intervention and therapy, water treatment systems, emergency breathing systems, welding operations, space-based delivery of liquids and gases, among others.
U.S. Pat. No. 6,089,027 issued Jul. 18, 2000 and U.S. Pat. No. 6,101,816 issued Aug. 15, 2000, both in the names of Luping Wang and Glenn M. Tom, describe a fluid storage and gas dispensing system including a storage and dispensing vessel for holding a fluid, such as for example a pressurized liquid whose vapor constitutes the fluid to be dispensed, or alternatively a compressed gas. The vessel includes an outlet port that is coupled to a dispensing assembly. The dispensing assembly may be of various forms, e.g., including a valve head comprising a dispensing valve and an outlet for selective discharge of gas from the vessel.
In the Wang et al. system, a fluid pressure regulator is associated with the outlet port and is positioned upstream of dispensed gas flow control means such as the aforementioned dispensing valve. The fluid pressure regulator is preferably at least partially interiorly disposed in the vessel, and most preferably is fully interiorly disposed therein, to minimize the possibility of impact and environmental exposure in use, as well as to permit a single weld or seam to be employed at the outlet port, to seal the vessel.
The regulator is a control device that is set at a predetermined pressure level, to dispense gas from the cylinder at such pressure level. In one embodiment of the aforementioned fluid storage and dispensing systems, a set point regulator is utilized and is pre-set at a single set point prior to its installation in the vessel. The pressure level set point may be superatmospheric, subatmospheric or atmospheric pressure, depending on the dispensing conditions, and the mode of gas discharge from the vessel. The vessel may optionally contain a physical adsorbent material having a sorptive affinity for the fluid contained in the vessel.
Such xe2x80x9cregulator in a bottlexe2x80x9d designs, including arrangements employing a double-stage (or multi-stage) fluid pressure regulator, optionally with a particulate filter assembly, provide an effective means and method for storage and dispensing of liquids and gases that are contained in the vessel at elevated pressure, e.g., at a pressure of from about 50 psig to about 5000 psig. The set pressure regulator is readily disposed in the interior volume of the storage and dispensing vessel, and effectively utilized to regulate the pressure and flow rate of discharged gas deriving from the contained fluid, in the fluid dispensing operation.
The regulator set point pressure is typically below 50 psig. Since the vessel is sealed in use, there is an inability to precisely measure the fluid remaining in the vessel as the dispensing operation proceeds.
Accordingly, while the xe2x80x9cregulator in a bottlexe2x80x9d fluid storage and dispensing system provides a safe and effective means for supplying fluids of widely varying type in industrial process applications, it would be desirable to provide a means and method of measuring internal pressure of the fluid in the storage and dispensing vessel.
Such internal pressure measurement would permit ready determination of the vessel""s fluid content and the approach to exhaustion of the vessel, but the fixed set point of the regulator in the vessel port prevents internal fluid pressure in the vessel from being directly measured exteriorly of the vessel. Although a pressure sensor or transducer element could be disposed in the interior volume of the vessel, in order to be functional, such element would have to be coupled to exterior monitoring means. This in turn requires a feedthrough in the valve head of the vessel, which requires leak-tight sealing and creates an additional leak path as a potential failure mode of the vessel.
In the absence of any means or method to determine internal pressure of the fluid in the sealed vessel of the fluid storage and dispensing system, there is corresponding concern on the part of the user that the vessel may be underfilled or overfilled for a given fluid-consuming operation.
There is also the possibility that the user will prematurely remove the fluid storage and dispensing vessel from the process facility before its full capacity is exhausted, in an effort to avoid xe2x80x9crunning dry,xe2x80x9d thereby underutilizing the fluid and wasting the fluid residuum in the vessel. In the case of many high-cost chemical reagents, such as those used in semiconductor fabrication, such underutilization results in a severe economic penalty that may very markedly affect the profitability of the industrial operation in which the dispensed fluid is being used.
In addition, if change-out of the fluid storage and dispensing vessels occurs only when the vessels are completely exhausted of the original fluid charge, without a reliable system for monitoring the internal pressure and hence the amount of fluid in the vessel, then significant loss of process equipment uptime may occur, as the vessels in the process system run dry. The system then must be idled to permit the change-out of the exhausted vessel. This non-monitored condition of the vessels is particularly problematic where a number of fluid supply vessels are employed to simultaneously supply different gases to a gas-consuming process unit. Such disruption of the gas supply incident to unexpectedly premature exhaustion of the fluid in the containment vessel can have significant negative impact on the efficiency and profitability of the overall process facility in which the fluid storage and dispensing system is employed.
It would be a significant advance in the art to provide a means and method of non-invasively monitoring the internal pressure of a sealed vessel containing fluid, which is amenable to use with fluid storage and dispensing systems of the type described in U.S. Pat. Nos. 6,089,027 and 6,101,816.
The present invention relates to a system for non-invasively monitoring the internal pressure of a closed vessel containing fluid, e.g., in a storage and dispensing system including a sealed fluid-containing vessel for supplying fluid useful in the manufacture of semiconductor products.
In one aspect, the present invention relates to a fluid containment system, comprising:
a vessel constructed and arranged to retain a fluid therein and to discharge fluid from the vessel in use or operation of the system;
such vessel including a vessel wall with an interior surface in contact with fluid contained in the vessel, and an exterior surface; and
a pressure monitor including a strain-responsive sensor disposed on the exterior surface and outputting a pressure-indicative response as fluid is discharged from the vessel, wherein pressure of the fluid in the vessel correspondingly changes with such discharge.
In one embodiment of the present invention, the outputted pressure-indicative response is strain (or deformation) in the vessel wall of said fluid-containing vessel. Pressure of the fluid contained by the vessel applies stress on the vessel wall of the vessel and subsequently causes strain/deformation in the vessel wall.
The resulting strain/deformation of the vessel wall in accordance with the invention is detected by a sensing device, such as an electrical resistance strain gauge, a piezoelectric element, a strain-sensitive calorimetric element, or a strain-sensitive matrix that contains latent strain-mediated chemical reactants.
A preferred strain-detection device useful in the practice of the present invention is an electrical resistance strain gauge assembly, which comprises one or more strain-measuring grids. The strain-measuring grid is subject to the same or proportional degree of strain/deformation as the vessel wall. The electrical resistance change in the strain-measuring measuring grid thereby enables monitoring of the strain and deformation, and correlative outputting of a signal indicative of pressure in the vessel.
In a specific preferred embodiment of the present invention, a Wheatstone bridge circuit is configured for accurately detecting and measuring electrical resistance change of the above-described strain-measuring grid. The Wheatstone bridge circuit incorporates the strain-measuring grid and achieves a balance of voltage in the circuit. Whenever the electrical resistance of the strain-measuring grid changes due to strain, even to a very small degree, the balance of the circuit is upset, and a resulting voltage difference scaled to the associated strain can be measured.
Such Wheatstone bridge circuit can be variously configured in any suitable manner. For example, the Wheatstone bridge circuit can be of a type incorporating a single strain-measuring grid and three standard non-measuring resistors; alternatively, it can incorporate two strain-measuring grids in adjacent bridge arms and two standard non-measuring resistors. In a preferred configuration, the Wheatstone bridge device comprises a xe2x80x9cfull bridge-configuration,xe2x80x9d wherein all four resistors of such Wheatstone bridge circuit are active strain-measuring grids. Additionally, multiple (redundant) sensor configurations, including but not limited to thermistor and amplifier componentry, may be employed to improve sensitivity, accuracy and reliability.
In another aspect, the invention relates to a fluid storage and dispensing apparatus, comprising:
a fluid storage and dispensing vessel enclosing an interior volume for holding a fluid, wherein the vessel includes a fluid discharge port for discharging fluid from the vessel;
a pressure regulating element in the interior volume of the fluid storage and dispensing vessel, arranged to flow fluid therethrough to the fluid discharge port at a set pressure for dispensing thereof; and
a pressure monitor including a strain-responsive sensor disposed on an exterior surface of the vessel and outputting a pressure-indicative response as fluid is discharged from the vessel, wherein pressure of the fluid in the vessel correspondingly changes with such discharge.
Yet another aspect of the invention relates to a method of monitoring pressure of a fluid in a vessel during use or operation involving discharge of fluid from the vessel, such method comprising:
sensing strain on a wall of the vessel; and
generating an output indicative of pressure of the fluid in the vessel correlative to the sensed strain of said vessel.
A still further aspect of the invention relates to a method of fluid management, comprising:
confining a fluid in a fluid storage and dispensing vessel including a vessel wall enclosing an interior volume for holding the fluid, wherein the vessel includes a fluid discharge port for discharging fluid from the vessel, and a pressure regulating element in the interior volume of the fluid storage and dispensing vessel, arranged to flow fluid therethrough to the fluid discharge port at a set pressure for dispensing thereof;
sensing strain of such vessel wall that is indicative of pressure of the fluid in the vessel; and
generating an output indicative of pressure of the fluid in the vessel correlative to the sensed strain of such vessel wall.
Other aspects, features and embodiments in the invention will be more fully apparent from the ensuing disclosure and appended claims.